ideas for levelling a concrete floor

I make some fabricated products, various bins, that are best built on the floor which means the floor should flat and level at to say the tolerance that a typical new slab (i.e. flat enough for welding, not metrology). The building is ancient and the floor is in poor shape and not very level. I can't afford to fix the entire thing but would like to fix some parts of it where we make these products. I know if I just skim over with concrete it it will quickly break up and I'm hoping for something less disruptive and costly than jack hammering out sections and repouring.

Are there any industrial, durable thin layer coatings we could apply over the top of the slab, creating say 10' x 10' area? The variation I'm dealing might only be 1/2 in some areas to 1.5 -2 in others

Any suggestions? Thanks

Epoxy.... something simple should be as low as $3/sq ft. Maybe slightly more since such a small area.

Might even be able to grind the existing concrete depending on age and hardness. Polish if you need a smooth surface. Sometimes with really old concrete no one wants to grind it because of the hardness tho. If you're getting up in the 30+ year old concrete... that might be an issue.

We had a company come in to lay sand mixed with epoxy and the floor was made flat and true,

Likey it was not dead flat like a lay-out plate.
I did meet a race car technician who had a lay-out table about 20' x 10'.

He put a Porsche race car on it and gave the car a very expensive chassis tune-up.

I would probably cut it out and pour new myself. Concrete is cheap and I have a small excavator, jackhammers and concrete experience.

One section of my shop is a barn floor that was poured in the 50's. It looked OK so I saved it, but once I started using that area my Forklift has broke through many times now. That concrete is a joke. 2" in one spot, 7" a few feet away. I'm tearing it all out this summer, fixing the subgrade and pouring new.

Mcgyver said:

I make some fabricated products, various bins, that are best built on the floor which means the floor should flat and level at to say the tolerance that a typical new slab (i.e. flat enough for welding, not metrology). The building is ancient and the floor is in poor shape and not very level. I can't afford to fix the entire thing but would like to fix some parts of it where we make these products. I know if I just skim over with concrete it it will quickly break up and I'm hoping for something less disruptive and costly than jack hammering out sections and repouring.

Are there any industrial, durable thin layer coatings we could apply over the top of the slab, creating say 10' x 10' area? The variation I'm dealing might only be 1/2 in some areas to 1.5 -2 in others

Any suggestions? Thanks

Click to expand...

Yes. Several. Next-door guy, one cycle ago, was a gang-boss for a firm that did very little else, day after day.

The stuff they use is FAST too, since their "niche" was to come in at closing time, work all night, have a zero lost-time refurbed premises open by morning. Retail space and such, of fair size, etc.

What they used is a self-leveling pourable GYPSUM product. And it works a treat!

Downside is THEY would lay tile or carpet over it. It wears waaay TF better than gypsum drywall, but does NOT wear as well as Portland Cement bound concrete.

His crew laid about 40 feet of 4 to 5 inch thick sidewalk with it for his residence. I had a chat with him that with no rebar, no expansion joints, no compacted gravel under, it would have a short life.

He just grinned.

It DID make about five years before it started to fall apart!

Long enough for he who knew it would do that to have sold-up and left the CURRENT owner grumbling!

Storal of the morey is that even EXPENSIVE shortcuts are still shortcuts.

You want"cheap" you gets it by doing it RIGHT.

- saw near the edges to insure de-coupling

- demo hammer it OUT.

- FIX the SUBGRADE.. it does 99.9% of the WORK.

Dividing the cost by... well looks like 40 years and easily as many more left in it for the superb slab the previous owner left ME with, 30 years this month and ISTR 8 or 9 years on his watch?

OTOH, he was not just a gang boss.

He was Vice President of a serious VDOT-spec highway paving company.

And VDOT does NOT put-up with the absolute shite Pennsyltucky considers a "road", either.

Quite the opposite.


TANSTAAFL.

I should have emphasized it more, parts tacked and welded in the surface, e.g. the inside corner of a bin wall gets welded to the the floor while the floor is on the ground. Epoxy is a great idea but I don't think its going to work with the welding

Mcgyver said:

I should have emphasized it more, parts tacked and welded in the surface, e.g. the inside corner of a bin wall gets welded to the the floor while the floor is on the ground. Epoxy is a great idea but I don't think its going to work with the welding

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Sounds like you need to set a large plate in the floor.

I have done details before for them, IIRC 2" burned holes on 24" c-c both ways.
Some blocks welded underneath for 2" of grout spacing.

Grout funnel sets in the holes, and you apply non-shrink grout.

I would agree that steel is the way to go. something between 1" and 2", self leveling grout underneath it.
Its the tried and true method, most older fab shops had steel floors. Mesta Machine, in Homewood, who built the rolls for steel mills, had a steel floor something like 300' long.

The advantage is, unlike concrete or epoxy, it has a resale value. Also, its a ground, weld a lug on somewhere near the welder, connect the ground cable, and anything metal is grounded.

I did a hybrid, where i inset 12" square 1" plate on an 8 foot grid, each with 4 holes tapped for 1" studs, flush with a new concrete floor. They are tied together in the concrete with 1" rebar, so if you screw a stud into one, attach the ground cable, every one of them is grounded to the weld circuit as well.
This is probably cheaper than steel, but requires either raising the floor (did that in one building, and it required forklift ramps, but otherwise worked well) or, chipping out existing concrete. Which is not that big of a deal, IF there are not a lot of ancient utilities under there.

I have always found that just biting the bullet, and ripping out the old stuff, whatever the project, is always faster, usually cheaper, and works better than trying to kludge a fix on something that has serious problems.

If the parts are near common just individual set-on blocks laser leveled..and mas so the set pad is replaceable when it gets buggered up with weld.

What Ries and Doug said. And many others. Loading dock and approach zone, up-top, the FL's tear it up.

But not only up-top. Plates are a common necessity in Hong Kong for *busy* loading dock approaches, ground-level as well.

They use SEA water for their 'crete.

It then get furrows and such on curves in carpark ramps and not-only.

Steel in ignorant flat"ish" plates is CHEAP, vs labour.
Takes a grid of drilled and/or tapped holes well, too.

PLAN for it, you could have a fast payback off time saved in production and easier meeting of QA spec's.

UGLYMRJ said:

Might even be able to grind the existing concrete depending on age and hardness. Polish if you need a smooth surface. Sometimes with really old concrete no one wants to grind it because of the hardness tho. If you're getting up in the 30+ year old concrete... that might be an issue.

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Up to an inch and a half thick will be a lot more than $3.00/sq. ft.

I used self leveling floor leveler on a floor that had cracked and sunk on one side from someone building a huge stone fireplace without proper footings. It was expensive, maybe about $40 for a 50# bag and that was probably at least 20 years ago. If you have any cracks in the existing floor make sure to put some tape over them because the leveler is like pouring syrup on the floor. It runs into the cracks. That mistake probably cost me an extra hundred dollars in leveler to fill the cracks.

Big B said:

I used self leveling floor leveler on a floor that had cracked and sunk on one side from someone building a huge stone fireplace without proper footings. It was expensive, maybe about $40 for a 50# bag and that was probably at least 20 years ago. If you have any cracks in the existing floor make sure to put some tape over them because the leveler is like pouring syrup on the floor. It runs into the cracks. That mistake probably cost me an extra hundred dollars in leveler to fill the cracks.

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That "leveler" that became penetration grout may also have saved that whole area from cracking again right away, too.

Even high-strength 'crete can only act like a bridge for but a short span.

Unless you build it like a real bridge or multi-story carpark.. the subgrade HAS to do the work.

Rent a decent plate tamper = save money on expensive slime.

Proper gradation and compacted lifts of aggregate and ordinary 'crete and re-bar can be a LOT cheaper.

Clean up the floor and roll out some epoxy in small areas that you can reach. Cover the "wet" epoxy with washed stone chips and let it cure. Vacuum or sweep up the loose stuff and you have a great surface to bond a skim layer to. Your results may vary.
Poured gypsum is not to be used. It is as durable as sheetrock without the paper.

Can a series of maybe 3'x3' tables me made and independently leveled with a transit to the same height?

Then you aren't working on a floor but still have room to walk between tables.

Easy enough to bolt bridges between well though out welding tables.

Scruffy887 said:

Clean up the floor and roll out some epoxy in small areas that you can reach. Cover the "wet" epoxy with washed stone chips and let it cure. Vacuum or sweep up the loose stuff and you have a great surface to bond a skim layer to. Your results may vary.
Poured gypsum is not to be used. It is as durable as sheetrock without the paper.

Click to expand...

I would imagine this would work well if you can get the epoxy to bond (concrete isn't nasty oil soaked crap)

One thing I did in a shop I rented was to cut a shitty slab into sections about 4x8 feet and dig a pit next to the slab a little bigger. Level and pack it real well. I flipped the slab pieces over so the smooth side was down and made sure it didn't rock (pretty easy). I dug the holes so the slab pieces would sit about 3" below the top of the new slab. I poured right over it with new concrete. I ran my business out of there for another 4 years and that slab did great. I figured it would crack in an outline of the slabs buried below, but it never did.

Things have changed for the better when it comes to concrete work. Diamond saw that slab up and get a small excavator to rip it out, and pour a new nice flat slab, nice and thick, plenty of reinforcing so the whole 10' x 10' is one monolithic piece that won't crack from loads on it, or settling. You'll be glad you did. I poured all the floors in our two 40x80 foot buildings back in the 70s and hand finished the whole thing. 6" of concrete on 5 feet of fill and not a crack any where after all these years.

Back in the day, one would set 2 rail road rails upside down.... dead level and pour the cement around them for a set up table in the floor...Phil

They sell floor leveling compound
Go look at Home Depot that stuff works if you do it right and fallow the directions
Go to the manufactures web site and pick the right one.